Nozzles for jet engines



3 Sheets-Sheet 1 Filed Feb. 13, 1967 Inventor I By 9: Su i a; A Home y H. M DONALD Oct. 8, 1968 3 Sheets-Sheet 2 Filed Feb. 15, 1967 Inventor H RY VkDONkLD By Bahia- A Home y United States Patent 3,404,842 NOZZLES FOR JET ENGINES Henry McDonald, Rocky Hill, Conn., assignor to British Aircraft Corporation (Operating) Limited, a British company Filed Feb. 13, 1967, Ser. No. 615,578 Claims. (Cl. 239265.37)

This invention relates to jet engine nozzles having an annular throat defined between a surrounding wall and a central plug, the plug having a rear face which is trans verse to the axis of the nozzle, so that the flow emerging from the throat is bounded internally by a streamline extending rearwards from the periphery of the rear face of the plug, while a body of dead air occurs within the streamline.

According to the present invention the nozzle includes a rearwardly-extending stern supported by the plug, the stem being thin relatively to the plug and supporting at its rear end a body which, in use, joins up with the streamline extending rearwards from the periphery of the rear face of the plug.

The body supported by the stem may take various forms. In one form, the body has a rear surface which is, roughly speaking, a paraboloid, and an annular front surface which is concave, so that the forward edge of the body is defined by the two surfaces meeting at a small angle.

In another form, the body is a hollow cylinder, with .a thin wall, open at its ends, supported from the stem by radial fins.

There may be means for adjusting the length of the stem to enable the longitudinal position of the body to be changed to suit different conditions of operation.

There may be means for adjusting the diameter of the body to suit different conditions of operation.

These adjustments may assist in controlling the thrust developed by the nozzle. v

The acocmpanying drawings show examples of nozzles according to the present invention. In these drawings:

FIGURE 1 is a longitudinal half section of one nozzle;

FIGURE 2 is a longitudinal half section of another nozzle;

FIGURE 3 is a fragmentary longitudinal section through mechanism for adjusting the length of the stem;

FIGURE 4 is a fragmentary longitudinal section through the body shown in FIGURE 1;

FIGURE 5 is a transverse section on the line VV in FIGURE 4;

FIGURE 6 is a fragmentary longitudinal section through the body shown in FIGURE 2; and

FIGURE 7 is a view. in the direction of the arrow VII in FIGURE 6.

FIGURE 1 shows approximate proportions which would be suitable for a jet engine nozzle with an overall diameter of about 50 inches. The throat 39 of the nozzle is defined between a surrounding wall 40 and a central plug 10. The means for supporting the plug 10 can be orthodox and are not shown. The plug has a rear face 41 transverse to the axis of the nozzle, and the plug supports a rearwardly extending stem 11. The stem supports at its rear end a body 45 in the form of a hollow cylinder, further details of which are shown in FIGURES 4 and 5. The flow emerging from the throat is bounded by streamlines 42 and 43. The streamline 43 joins up with the external surface of the body 45, and a further streamline 47 extends rearwards from the body. There are recompression shock waves as indicated at 46 and 49.

Air within the spaces 44, 48 and 50 forms a single circulating body of dead air. The circulation is indicated roughly by arrows. This air exerts a forward pressure on the transverse rear face 41 of the plug. The presence of the body 45 serves to augment this pressure. If the body were absent, the streamline 43 would break down (a behaviour otherwise known as stagnation) as it approaches the centre line of the nozzle. The body 45 is placed slightly downstream of the position at which the streamline would otherwise break down.

In the nozzle shown in FIGURE 2, there is again a surrounding wall 40 and a plug 10 with a rear face 41, supporting a stem 11. The body 52 supported at the rear end of the stem is in this case a solid having a rear surface 53 which resembles a paraboloid and an annular front surface 54 which is concave. Thus the body has a forward edge 55 defined by the two surfaces 53 and 54 meeting at a small angle. The streamline 43 joins up with the surface 53. There is a recompression shock at 52. Dead air circulates within the space 44.

FIGURE 3 illustrates a translating mechanism housed within the nozzle plug10. The stem 11 is located in a series of recirculating ball systems 12 arranged longitudinally and is translated by means of driven gears 13 meshing with a rack system 14. A coaxial shaft 15, rotated by a motor .16, and with a splined connection 17 along its length to allow for translation of the stem, provides a rotary movement to achieve variation in diameter of the body 45 (FIGURE 1) or 51 (FIGURE 2).

Referring to FIGURES 4 and 5, the shaft 15 has a screw thread 18 formed upon it on which cooperates a nut 19. Lugs on the nut provide anchorages for links 20. These links each are pivotally connected to further links 22 and engage in slots 21 in radial vanes 23. The further extremities of links 22 are pivoted to the fixed support 24 for-the shaft 15. Each vane 23 is capable of radial movement in guideways 25 and 26. Each vane terminates in a T member 27, forming part of the periphery of the cylindrical body 45 FIGURE 1, each T member having slots 28 formed longitudinally in each extremity. In these slots are located resilient metal members 29 which can adjust to the contour of the cylinder irrespective of its diameter.

FIGURES 6 and 7 illustrate a similar rotatable shaft 15 on which is formed a screw thread 30. A nut 31 cooperates with this thread and has lugs 32 to which links 33 are pivotally attached. The extremity of each link connects with a pivoted flap 34, of which four are illustrated but for aerodynamic reasons more may be required. Each flap is pivoted to the remainder of the body, and in its mid-position conforms closely with its contour.

I claim:

1. A jet engine nozzle including: an annular throat defined between a surrounding wall and a central plug, the plug having a rear face which is transverse to the axis of the nozzle; and a rearwardly-extending stern supported by the plug, the stem being thin relatively to the plug and supporting at its rear end a body which, in use, joins up with a streamline extending rearwards from the periphery of the rear face of the plug.

2. A nozzle according to claim 1, in which the body has a rear surface which resembles a paraboloid, and an annular front surface which is concave, so that the forward edge of the body is defined by the two surfaces meeting at a small angle.

3. A nozzle according to claim .1, in which the body is a hollow cylinder, with a thin wall, open at its ends, supported from the stem by radial fins.

4. A nozzle according to claim 1 including means for adjusting the length of the stem.

5. A nozzle according to claim 1, in which the body is adjustable in diameter.

- 4- References Cited UNITED STATES PATENTS 2,557,883 6/1951 Miller 239265.33 3,012,400 12/1961 Corson 239--265.11

M. HENSON WOOD, JR., Primany Examiner.

V. M. WIGMAN, Assistant Examiner. 

1. A JET ENGINE NOZZLE INCLUDING: AN ANNULAR THROAT DEFINED BETWEEN A SURROUNDING WALL AND A CENTRAL PLUG, THE PLUG HAVING A REAR FACE WHICH IS TRANSVERSE TO THE AXIS OF THE NOZZLE; AND A REARWARDLY-EXTENDING STEM SUPPORTED BY THE PLUG, THE STEM BEING THIN RELATIVELY TO THE PLUG AND SUPPORTING AT ITS REAR END A BODY WHICH, IN USE, JOINS UP WITH A STREAMLINE EXTENDING REARWARDS FROM THE PERIPHERY OF THE REAR FACE OF THE PLUG. 